Hydrogen Bonds

The energy of covalently bonded H-O is about 492kJ/mol, but it still have addition attraction to form hydrogen bond of energy of 23kJ/mol.Water's hydrogen bonding holds water molecules up to about 15% closer than if water was a simple liquid with just van der Waals dispersion interactions.The hydrogen bond in water is part (about 90%) electrostatic and part (about 10%) covalent.Clusters linked by extensive hydrogen bonding can be considered as being connected by extensive, but complementary, electron delocalization. As electrons are not held by individual molecules but are easily distributed amongst water clusters they can give rise to coherent regions.
Hbond delocalization
The strongest hydrogen bonding in water existing in the short linear proton-centered H5O2+ ion at about 120 kJ mol-1.